These questions are boundary problems. Identify the driver's class, the substance being considered and whether the question asks when driving becomes prohibited or how an offence is classified.
Build the alcohol range before naming the offence
For an ordinary driver, the blood-alcohol prohibition begins at 0.50 g/L. For a learner or probationary driver, it begins earlier, at 0.20 g/L. The lower number is not a statement that a small amount is safe, and safety advice may still be to avoid alcohol entirely. It is the statutory boundary used in these rules. Once you have the correct lower boundary, place the measured value into a range. From that applicable boundary up to, but not including, 0.80 g/L, the offence is a fourth-class contravention. At exactly 0.80 g/L, the upper range begins and the conduct is a délit. The equality sign belongs with the more serious category.
| Fact to identify | How to reason |
|---|---|
| Ordinary driver | Use 0.50 g/L as the lower blood-alcohol boundary. |
| Learner or probationary driver | Use the lower 0.20 g/L boundary. |
| Below 0.80 g/L but at or above the applicable boundary | Classify it as a fourth-class contravention. |
| At least 0.80 g/L | Classify it as a délit. |
| Narcotic use established by analysis | Do not invent a permitted small quantity or a collision condition. |
| Legally required alcohol verification | The refusal itself supplies the délit classification. |
Keep the narcotics rule separate from the alcohol scale. When analysis establishes use of a classified narcotic, the rule does not supply a permissible measured amount below which driving is allowed. Nor does it wait for a collision. A lawful verification request is another distinct branch: refusing it is classified by the refusal itself.
Common confusions
- Replacing the probationary threshold with 0.00 g/L because zero alcohol is sensible safety advice. The legal boundary tested here is 0.20 g/L.
- Treating 0.60 g/L for an ordinary driver as no road offence or merely a warning. It lies in the fourth-class contravention range.
- Leaving exactly 0.80 g/L in the lower range. The délit boundary includes equality.
- Adding a crash requirement or a supposedly harmless measured quantity to established narcotic use. Neither condition belongs to the rule.
Try it
At a lawful roadside alcohol check, a driver refuses the legally required alcohol verification. How is that refusal classified?
- A délit
- No offence without a crash
- A voluntary choice
- Only a paperwork warning
For an ordinary driver, from what blood-alcohol concentration is driving prohibited? Enter the number in g/L.